The present invention relates to liquid ejection apparatuses ejecting liquid as droplets through liquid ejection heads, such as inkjet recording apparatuses, display manufacturing apparatuses, electrode manufacturing apparatuses, and biochip manufacturing apparatuses, and liquid filling methods for these apparatuses.
Conventionally, inkjet printers are known as liquid ejection apparatuses that eject liquid droplets through nozzles of an ejection head. There are some inkjet printers (hereinafter, “printers”) that include “off-carriage” type ink supply systems. One such system includes an ink retainer retaining the ink as liquid that is installed outside a carriage of the printer.
As described in Japanese Laid-Open Patent Publication No. 2003-211688, for example, the ink supply system may include an ink supply line that extends from an ink cartridge to an ejection head formed in the carriage. The supply line includes a pressure adjustment mechanism as well as a tubular passage.
Typically, the pressure adjustment mechanism is formed by, for example, a self-sealing valve having a pressure adjustment valve and a pressure chamber. A choke valve is arranged between the pressure adjustment mechanism and the ink cartridge in the supply line.
Before the initial use of such a printer, initial ink filling is performed for charging the ink into the supply line. More specifically, a nozzle surface of an ejection head is sealed by a cap and, in this state, the interior of the cap is depressurized. This draws the ink from the ink cartridge into the supply line, thus filling the line.
When the initial ink filling is performed on the printer, it is crucial that the ink be supplied to the supply line without forming bubbles (an air layer) in the supply line.
However, the supply line includes enlarged portions such as the pressure chamber of the pressure adjustment mechanism and a head filter chamber. Each of these enlarged portions has an enlarged communication area compared to that of the tubular passage. This may facilitate formation of the bubbles (the air layer) in the enlarged portions, thus hampering the initial ink filling into the supply line.
To solve this problem, the initial ink filling involves choke suction. The choke suction is performed with a choke valve held in a closed state (in a choked state). This increases the negative pressure acting in a downstream section of the supply line from the choke valve. The air is thus removed from the pressure chamber or the like in the supply line. At this stage, by opening the choke valve, the ink is efficiently charged into the supply line.
Nonetheless, by such choke suction, the bubbles that have been removed from the pressure chamber of the pressure adjustment mechanism may be re-trapped in the head filter chamber located downstream from the pressure chamber. In this case, by repeating the choke suction to obtain an equal level of negative pressure to that of the previous choke suction, the trapped bubbles can be removed from the head filter chamber through an ejection head. However, the repeated choke suction may again remove the bubbles from the pressure chamber and then re-trap these bubbles in the head filter chamber.
The amount of the bubbles trapped in the pressure chamber of the pressure adjustment mechanism can be decreased by repeating the choke suction. However, in order to reduce the bubbles trapped in the head filter eventually to a level necessary for maintaining the printing quality, the choke suction must be repeated for multiple times, wasting an excessive amount of ink. This hampers efficient filling of the ink, or the liquid.
Similar problems occur in different types of liquid ejection apparatuses ejecting liquid as droplets by ejection heads, other than the printers, as long as the apparatuses include an enlarged portion having a communication area larger than that of the tubular passage. These apparatuses include display manufacturing apparatuses, electrode manufacturing apparatuses, and biochip manufacturing apparatuses.